With the recent advancements in hard disk drive (HDD) design toward high-density recording, the physical sector format of HDDs has been migrating from 512 bytes per sector to 4096 (4K) bytes per sector. Many of the existing software components, on the other hand, assume that the HDDs are configured with 512-byte logical sectors, and here arises an issue of compatibility between their assumption and the native 4K-byte sectors of HDDs. Those 4K-native HDDs are supposed to operate only with 4096-byte logical sector mapping, but the 512-byte logical sectors are not directly mapped onto their 4096-byte physical sectors. A known solution for this problem is the 512e mode of the Advanced Format Technology (AFT). In this 512e mode, 4K-native HDDs emulate operation in the conventional 512-byte sector organization, thus enabling the existing software components to access data in those HDDs. See, for example, the following publications:
Japanese Laid-open Patent Publication No. 2012-221350
Japanese Laid-open Patent Publication No. 2005-63441
Japanese Laid-open Patent Publication No. 2010-26345
Japanese Laid-open Patent Publication No. 2010-211888
Japanese Laid-open Patent Publication No. 2010-80021
One thing to note about the AFT 512e mode, however, is that HDDs execute a read-modify-write (RMW) cycle in response to a write command, when its write data boundaries are not aligned with the 4096-byte physical sector boundaries. RMW cycles include a read operation before writing data, which means that the write operation is delayed by a multiple of the rotation time of disk media (e.g., two rotations). This delay degrades the performance of HDD access.